The incidene of cancer markedly increases with advancing age. We hypothesize that this increase is in part, a result of age-related alterations in the metabolism of omnipresent chemical carcinogens. Previous work from our laboratory has shown that the rate of metabolism of the carcinogen 3,4-benzo(alpha)pyrene (BP), as determined by fluorimetric methods, declines with advancing age. However, the metabolites of both BP and 2-aminofluorene, generated by hepatic tissues obtained from senescent rats, are of greater mutageneity in a Salmonella test system than are those metabolites generated by tissue samples obtained from younger animals. We wish to expand these studies to determine whether these potentially very important findings are of general applicability. Therefore, we propose to study the effects of senescence upon the metabolism of BP in other rat tissues, such as skin and lung, which are more relevant target organs for polycyclic aromatic hydrocarbons (PAH) carcinogenesis. We will also determine the kinetics of metabolism of BP in various tissues obtained from C57BL/6J male mice of different ages. Finally we shall examine the effects of aging upon aryl hydrocarbon hydroxylase (AHH) activity in cultured human lymphocytes.